Roller skating is the traveling on smooth terrain with roller skates. It is a form of recreation as well as a sport, and can also be a form of transportation. Skates generally come in two basic varieties: quad roller skates and inline skates or blades, though some have experimented with a single-wheeled "quintessence skate" or other variations on the basic skate design.
During the late 1980s and early 1990s, the Rollerblade-branded skates became so successful that they inspired many other companies to create similar inline skates, and the inline design became more popular than the traditional quads. The Rollerblade skates became synonymous in the minds of many with "inline skates" and skating, so much so that many people came to call any form of skating "Rollerblading," thus becoming a genericized trademark. For much of the 1980s and into the 1990s, inline skate models typically sold for general public use employed a hard plastic boot, similar to ski boots.
In or about 1995, "soft boot" designs were introduced to the market, primarily by the sporting goods firm K2 Inc., and promoted for use as fitness skates. Other companies quickly followed, and by the early 2000s the use of hard shell skates became primarily limited to the Aggressive inline skating discipline.